Nasal mask



FIG. 1 is a front view of a nasal mask showing the new design;

FIG. 2 is a back view of the design shown in FIG. 1;

FIG. 3 is a side view of the design shown in FIG. 1, each side being a mirror image of the other;

FIG. 4 is a bottom view of the design shown in FIG. 1; and,

FIG. 5 is a top view of the design shown in FIG. 1.

The portions of the Figures shown in phantom lines are not part of the claimed design but are for illustration only. 

The ornamental design for a nasal mask, as shown and described. 